The radio-frequency wireless transceiver chip of the existing technology includes three implementation schemes, i.e., superheterodyne (double frequency-conversion), low-medium-frequency (single frequency-conversion), and zero-medium-frequency. Based on double frequency-conversion that works in the frequency band of 2.4 GH ISM, this invention proposes a smart frequency distribution scheme that is flexibly and successfully used in the radio-frequency SIM card of a radio-frequency handheld terminal.
As compared with the scheme adopted by the existing technology in the frequency band of 2.4 GHz ISM, this invention has the following advantages: it improves the signal image frequency to approximately 3 GHz through smart frequency distribution without using an external image rejection filter. As the frequency band of 3 GHz is rarely used, this effectively solves the image rejection problem in the application of 2.4 GHz ISM frequency band. It is used successfully in a radio-frequency SIM card.
The existing technology for frequency conversion has the following disadvantages: when a radio-frequency SIM card is used in the 2.4 GHz ISM frequency band, an external filter is needed to solve the image rejection problem in the actual application, and power consumption of the chip is relatively high.